The orthogonal frequency division multiplexing (OFDM) technology is a widely applied multi-carrier modulation technology. A data stream is split into a plurality of parallel subcarriers for transmission, and each subcarrier may have a relatively low data rate whereas a relatively high transmission rate is achieved on the whole. A disadvantage of OFDM is that OFDM has relatively severe out-of-band leakage, because a subcarrier waveform of OFDM is a sinc function with relatively severe out-of-band leakage. In a Long Term Evolution (LTE) system, a guard band that is 10% of a frequency spectrum needs to be reserved to ensure that there is no interference to an adjacent system. In addition, in OFDM, all subcarriers are required to achieve strict frequency synchronization and relatively good time synchronization. For this reason, OFDM has the following problems: A subcarrier spacing, a symbol length, a cyclic prefix (CP) length, and the like of OFDM need to keep consistent within Long Term Evolution (LTE) system bandwidth. For multi-user uplink OFDM transmission, signals sent by user equipments (UE) that occupy different subbands need to arrive at a base station (BS) almost at the same time, so as to meet a time synchronization requirement. In LTE, this objective is achieved through adjustment of a timing advance (TA), but relatively high signaling overheads are generated in a TA adjustment process. These problems restrict the LTE system from having a more flexible air interface design.
The foregoing problems are resolved after emergence of filtered orthogonal frequency division multiplexing (F-OFDM). F-OFDM is a new multi-carrier technology. In F-OFDM, system bandwidth is divided into a plurality of independent subbands through subband filtering. Different parameters such as the subcarrier spacing, the symbol length, and the CP length can be used in different subbands, and a method is provided to resolve intersymbol interference caused by a filter. Therefore, for each subband, most appropriate OFDM parameters can be selected based on a channel scenario or a service type, to achieve higher performance.
System bandwidth can be divided into a plurality of subbands by using the f-OFDM technology, and different subcarrier spacings can be used on different subbands. However, there is no ready-made method to resolve a frequency location relationship between subbands. As viewed from principles of the f-OFDM technology, the location relationship between subbands may be any relationship, but different methods have different complexity in signal processing and protocol processes.